1. Technical Field of the Invention
The present invention relates to an apparatus and methods for manufacturing hot rolled steel sheets, using continuous casting equipment and a plate reduction press apparatus, with a high production efficiency, high quality and low cost.
2. Prior Art
1. According to the prior art of manufacturing hot rolled steel sheets, steel sheets (strips) are manufactured by hot rolling a continuously cast slab; the slab is reheated in a heating furnace, rough and finish rolled to a predetermined plate thickness, cooled on a runout table to a predetermined temperature, and then reeled into a coil using a coiler.
Such a conventional rolling system known in the prior art and described above (called xe2x80x9cbatch rollingxe2x80x9d for short) leaves the worked material in an untensioned state during the period from the time that the leading end of a hot rolled steel sheet leaves a group of finish rolling mills to the time it is coiled by a coiler, and during the period from the time that the trailing end of the hot rolled sheet leaves the group of finish rolling mills to the time that it has been completely coiled in the coiler, and as a consequence, particularly with a thin steel sheet, the leading and trailing ends of the sheet become extremely distorted with a wave shape on the runout table. As a result, the leading and trailing ends of the steel sheet are not cooled satisfactorily and the quality of the material often become defective, which may lead to a reduction in product yield.
In batch rolling, the maximum length of a hot rolled steel sheet depends on the maximum dimensions of a slab that can be rolled, that is, the thickness and length of a slab that,can be inserted into a heating furnace. In addition, because the trailing end of a steel sheet moves unstably on the runout table during batch rolling as described above, the speed of rolling the leading end is reduced to about 600 mpm, and after the leading end of the steel sheet has been reeled onto the coiler, the speed is increased to the normal rolling speed of more than 1,000 mpm, then immediately before the trailing end of the steel sheet leaves the group of finish rolling mills, the speed is decreased, according to a predetermined sequence of controlling the speed. As a result, the time taken to roll the entire steel sheet is longer than the time it would have taken to roll the steel sheet from the leading end to the trailing end at the normal, constant speed, so consequently the production efficiency is low. Furthermore, there is an idle time between rolling one steel sheet and rolling the next steel sheet, which further aggravates the production efficiency.
In contrast to such a batch rolling process as described above, a rolling method has been proposed in which a slab with a plate thickness of less than 100 mm is cast continuously, rolled through all the stages up to finish rolling without cutting the slab at all, and after the slab has been made into a hot rolled steel sheet with a redetermined plate thickness, the sheet is cut. However, because the production capacity of a continuous casting machine is lower than that of a rolling mill, this method cannot yield a satisfactory throughput.
Under these circumstances, various methods have been proposed in the prior art, aimed at avoiding the problem of the low yield in batch rolling and assuring high productivity, regarding the methods of manufacturing hot rolled steel sheets using a slab with a plate thickness of more than 100 mm.
First, to solve the problem of the low yield caused by defective material in the leading and trailing ends of a hot rolled steel sheet, a method is proposed in which the trailing end of a preceding sheet bar (after the material has been rough rolled) and the leading end of the present sheet bar are joined together, and a plurality of sheet bars are continuously finish rolled to produce a hot rolled steel sheet (called the xe2x80x9ccontinuous hot rolling methodxe2x80x9d for short).
With this method of continuous hot rolling, when n sheet bars are joined into one steel sheet, for example, the steel sheet is subjected to a constant tension between the finish rolling mill and the coiler, therefore when the steel sheet formed from n coils of steel sheets is rolled, material defects due to wave distortions on the runout table are produced only in the portion corresponding to the leading end of the first coil, and the other portion corresponding to the trailing end of the n-th steel coil, so that compared to batch rolling, the yield is higher. In addition, the low-speed rolling operation to keep the leading and trailing ends of the steel sheet moving stably on the runout table is required only for the portions corresponding to the leading end of the first coil and the trailing end of the n-th coil, and the other portions of the steel sheet can be rolled at a normal, constant speed, therefore compared to batch rolling, the rolling time is shorter and the efficiency of production is correspondingly higher. Moreover, there is no idle time during rolling of the entire steel sheet comprised of individual sheet bars joined together, which also contributes to a higher efficiency of production.
However, the roughing-down rolling used in this continuous hot rolling method is the same as that of batch rolling, so that planar, defective shapes known as tongues or fish tails are produced at the leading and trailing ends of each sheet bar. Consequently, before joining sheet bars, such planar defects at the leading and trailing ends of each sheet bar must be removed before finish rolling. Therefore, assuming n slabs are rough rolled, when the n sheet bars are joined, 2n portions (crops) are cut off (the number of such crops is the same as for batch rolling), so a reduction in the yield concerned cannot be avoided. In addition,. when joining sheet bars, portions to be joined must be heated, so defective material caused by the effects of heating, occur, although the effect is slight. Also the strength of the joints in the sheet bars is adversely affected in the continuous hot rolling method and may be so low that the production line might be stopped accidentally because a joint breaks during finish rolling.
When a slab is cast continuously, cut losses are produced during slab cutting and finishing, but the continuous hot rolling method gives rise to the same amount of cut losses as the batch rolling method because the length of the slab is identical to that used in batch rolling. In addition, when only slabs taken from one heating furnace are used in the continuous hot rolling method, a 100% efficiency of the rolling mill cannot be achieved, since the heating efficiency of the heating furnace is lower than the rolling efficiency of the rolling mill.
The unexamined Japanese patent publication No. 106403, 1982 proposes a line of continuous hot rolling facilities in which the ends of a preceding slab and the present slab are joined together, and the joined slabs are continuously rolled by a group of planetary mills and another group of finish rolling mills.
In this system, the slabs are connected together and rolled continuously, so the reduction of the yield caused by crop cutting can be avoided, but because the strength of the joints is low as in the case of the unexamined Japanese patent publication No. 89190, 1992, the joint may possibly break during rolling.
The unexamined Japanese patent publication No. 106409, 1982 proposes continuous hot rolling facilities in which a slab produced by a rotary caster is rolled continuously by a group of planetary mills and another group of finish rolling mills, and the unexamined Japanese patent publication No. 85305, 1984 offers a continuous hot rolling line in which a slab is produced by a rotary caster, the slab is rolled by a cast rolling mill, and after the rolled slab has been reeled up once inside a coil box, it is rolled to a predetermined plate thickness by a group of finish rolling mills.
The aforementioned unexamined Japanese patent publication No. 85305, 1984 describes that a slab with a thickness of about 200 mm can possibly be cast at a maximum speed of about 10 mpm using a rotary caster, but no such result has been reported so far, therefore this system cannot be applied in a practical hot rolling line aimed at high productivity, at least at present. In addition, this system has such difficulties as cracks produced during casting and the difficulty of applying the system to make a slab with a rectangular section.
The planetary mills and the cast rolling mills cited in the above-mentioned unexamined Japanese patent publications Nos. 106409, 1982 and 85305, 1984 are problematic in various aspects which will be detailed later, so these mills cannot be applied easily to a practical hot rolling process.
The unexamined Japanese patent publication No. 92103, 1984 proposes a rolling system in which the maximum work volume of one charge of a converter is cast continuously, and the continuously cast slab is formed into a sheet bar using a large-reduction rolling mill, and is reeled in an up-end state into a sheet bar coil, and the sheet bar coil is unwound and finish rolled by a subsequent rolling mill into a predetermined plate thickness, and the coil is cut when it is unwound by the coiler.
According to the rolling method of this unexamined Japanese patent publication No. 92103, 1984, a long slab with a maximum length corresponding to one charge of a converter is rolled, so there are only two crop portions to be cut off, i.e., the leading and trailing ends of the slab, hence the method provides the advantage that the reduction of yield that accompanies crop cutting and slab cutting is smaller than with the above-mentioned continuous hot rolling method. In addition, according to the proposal of the publication, the facilities are configured with a continuous casting machine, a plurality of rough rolling mills and a finish rolling line, in which a group of rough rolling mills supply the single finish rolling line with sheet bar coils, to prevent a reduction in rolling efficiency due to the imbalance between the production capacity of the continuous casting equipment and the production capacity of the finish rolling line (normally, the capacity of continuous casting is less than the capacity of finish rolling).
However, when a sheet bar is wound up once in an upended ended state and unwound in this rolling system, the sheet bar must be twisted through 90xc2x0, therefore a facility for twisting the sheet bar is needed. Moreover, the approximate dimensions of a continuously cast slab with a weight of loot, for instance, are 1,000 mm widexc3x97250 mm thickxc3x9750 m long, and when the slab is pressed to a sheet bar coil, the diameter and weight of the coil is more than 4 m and 100 t, respectively, so that the coiling facilities become extremely large. Also, when a sheet bar is coiled, the surfaces of the sheet bar rub against each other and are scratched, resulting in flaws on the surface, and a hot rolled steel sheet with a good surface finish can no longer be manufactured, which is another problem associated with this rolling system.
2. In a hot rolling line in which a hot rolled steel sheet is to be manufactured from a hot slab with a high productivity, the normal practice is that a continuously cast slab (normally with a minimum thickness of 100 mm) is reheated while it is still hot or after it has once cooled down, or the continuously cast slab is directly transferred as a hot slab. In a roughing-down mill, i.e. the first rolling process of hot rolling, the hot slab is rolled through several passes with rolls of about 1,000 to 1,200 mm xcfx86 in diameter, into a sheet bar of about 15 to 50 mm in thickness, and then the sheet bar is rolled in a finish rolling process, the second rolling process, to a predetermined thickness, thus a hot rolled steel sheet is manufactured.
In the method of hot rolling a slab as described above, the temperature of the material during rolling varies depending on the temperature rise due to the heat caused by processing and the heat lost to the press rolls. In a normal roughing mill, the heat lost to the press rolls is greater because of the long length of material in contact with the rolls. Furthermore, when a plurality of passes of rough rolling are used, the material is in a so-called air-cooling state between each rolling pass, so that the temperature of the material decreases. Consequently, a considerable amount of the heat contained in the hot slab before the beginning of rolling is lost during a conventional rough rolling process known in the prior art.
As a result, in a system with a line of conventional hot rolling mills, it is difficult to maintain the temperature of the material at the beginning of finish rolling, in particular for a rolling process for manufacturing a thin sheet with a thickness of 2 mm or less, the temperature of the material decreases considerably during the finish rolling process, so that it is sometimes difficult to maintain the temperature of the material above the Ar3 point at the outlet of a finish rolling process.
To solve these problems, according to the prior art, a rolling system in which the heat loss is kept to a minimum by rough rolling the material at a high speed was developed, but this rolling system cannot be applied in practice because of the high equipment cost, in particular the driving system is very expensive.
A cast slab with a thickness of 100 mm or more is often accompanied by internal defects such as voids near the center part of the thickness of the slab, however, these defects cannot be easily eliminated by ordinary rough rolling because the slab is rather thick compared to the length of the contact arcs between rolls and the material, so the pressing strains cannot penetrate easily to the center part of the plate thickness. Consequently, there is the fatal problem that the internal defects still remain at the end of a finish rolling process, in the worst case.
3. A rolling system that rolls a so-called medium-thickness slab with a thickness of 50 mm to 150 mm, manufactured and supplied from a continuous casting machine, and rolled down to a thin sheet, is normally composed of rough rolling facilities for rolling the slab to a thickness of about 20 mm, and finish rolling facilities in which the slab is next rolled to a thickness of about 1 to 2 mm. Various configurations of rolling systems with such rolling facilities are known in the prior art.
FIG. 1 is an example of a configuration of conventional rolling facilities. The rolling facilities 1 shown in this figure are provided with table rollers 3 that carry and transport along a rolling line, a medium-thickness slab 2 manufactured by a continuous casting system in a batch line, not illustrated, and cut into a predetermined length (for instance, a length of 30 m with a plate thickness of 90 mm), a walking furnace 4 that houses and heats the slab 2 to a predetermined temperature, a plurality of rough rolling mills 6 (two mills in this figure) composed of vertical roll stands 5 at the inlet of the line, and an intermediate coiler 7 which winds and unwinds the rough rolled material in order to maintain the temperature of the material. The intermediate coiler 7 is provided to prevent the leading end of the slab 2 from being cooled while it is being rolled with the rough rolling mills 6 etc. or during transportation on the table rollers 3, and to prevent deformation of the shape of the slab due to heat strains, and the coiler first reels the slab with a thickness of 2 of 20 mm and then unwinds the slab from the trailing end thereof and sends it in the downstream direction.
In addition, as shown in FIG. 1, the rolling facilities 1 are provided with a plurality of finish rolling mills 9 (5 mills in this figure) with a vertical roll stand 8 at the inlet, and a plurality of down coilers 12 that wind the material 2xe2x80x2 being pressed into a coil, in which the conveyed slab 2 is finish rolled by the finish rolling mills 9 to a product thickness of about 1 to 2 mm, and after being cut by a shear machine 10, the material 2xe2x80x2 after being pressed is reeled into a coil by a coiler 12, through the pinch rolls 11.
Furthermore, the unexamined Japanese patent publication No. 90303, 1988 proposes a xe2x80x9cHot rolling apparatusxe2x80x9d in which the group of rough rolling mills is omitted from an apparatus for rolling a medium-thickness slab. As shown in the schematic view of FIG. 2, this hot rolling apparatus 15 is composed of a heating and holding furnace 16, and on the downstream side of the heating and holding furnace 16, a coil box 17, a crop shear machine 18, a group of finish rolling mills 19 with five finish rolling mills F1 to F5, edgers E1, E2 at the inlet and outlet of F1, and a down coiler 20 at the end farthest downstream. F1 and F2 are reverse rolling mills that can roll a slab 21 backwards and forwards.
However, with the conventional rolling apparatus for a medium-thickness slab shown in FIG. 1, there are problems such as (1) to manufacture a slab with a thickness of about 20 mm, two rough rolling mills and an intermediate coiler for heating and holding are required, so the rolling line becomes so long that its cost is increased, (2) because a slab with a thickness of about 20 mm is rolled by rough rolling mills at a high speed in order to keep its temperature high, the rough rolling mills cannot be arranged to operate continuously (in tandem) with a finish rolling mill, (3) even when an intermediate coiler is provided, the slab must be reversed by coiling and uncoiling, therefore the temperatures of the leading and trailing ends and of both edges of the slab are not distributed evenly, so that the yield of the material to be pressed may often be low, and (4) consequently, very thin sheets (0.8 to 1.0 mm) for which there is a high demand cannot be manufactured with this apparatus.
On the other hand, the conventional hot rolling apparatus shown in FIG. 2 provides a fairly short rolling line by omitting the group of rough rolling mills, but it is accompanied by various problems such as (1) when a slab is reverse rolled with a reverse rolling mill, the surface temperature of the material being rolled decreases so much that rolling becomes difficult, (2) the temperatures of the leading and trailing ends and the edges of the material being rolled are unevenly distributed, resulting in a low yield of the material being rolled, and (3) a coil box is required.
4. Conventionally, the maximum length of an ordinary slab is about 12 m, but recently, a long slab with a length of more than 100 m can be manufactured by a continuous casting system.
However, there was no such equipment that could roll a slab with an ordinary length and a long slab, by hot rolling to produce a thin sheet, so there has been a demand for such equipment. With a long slab, there were no such facilities that could manufacture coils with various plate widths and plate thicknesses, wound separately according to each type of width and thickness, from a slab, therefore there has also been a demand for this type of equipment.
5. Moreover, with an ordinary rolling mill in which a material to be rolled is rolled between two work rolls, normally the reduction ratio is limited to about 25%. Consequently, a high reduction ratio cannot be achieved when a material is rolled in a single pass (for instance, reducing the material from about 250 mm to a thickness of 30 to 60 mm), therefore for this purpose, a tandem rolling system in which three or four rolling mills are arranged in tandem, or a reverse rolling system in which the material to be rolled is rolled backwards and forwards, are used in practice, however, there are problems such as that a long rolling line is needed.
In addition, a planetary mill, Sendzimir mill, cluster mill, etc. has been proposed as rolling methods that enable high-reduction pressing in one pass. However, with these rolling means, small diameter rolls press the material to be rolled at a high speed, and are accompanied with various problems such as large impacts, short life of bearings etc., unsuitability for mass production facilities, and so on.
To solve the above-mentioned problems, kinds of press apparatus modified from a conventional stentering press machine have been proposed for reducing the thickness of a plate (for instance, Japanese patent publication No. 014139, 1990, unexamined Japanese patent publication No. 222651, 1976 and unexamined Japanese patent publication No. 175011, 1990).
In the unexamined Japanese patent publication No. 175011, 1990 xe2x80x9cFlying sizing press apparatusxe2x80x9d shown in FIG. 3, rotating shafts 32 are arranged above and below or to the left and right of a transfer line Z of a material to be shaped, and the eccentric portions of these rotating shafts 32 are connected to the bosses of rods 33 with a predetermined shape, and dies 34 are connected to the tips of the rods 33, on opposite sides of the transfer line of the material to be shaped, in which the rotating shafts 32 are rotated, and the dies 34 are moved to press the material 31 to be shaped (material to be reduced) from above and below the transfer line through the rods 33 connected to the eccentric portions of the rotating shafts, thereby the thickness of the material 31 to be shaped is reduced.
However, a conventional plate reduction press apparatus, an example of which is shown in FIG. 3 has a problem in that there are difficulties with the transfer speed of the material 31 to be pressed, although the apparatus can achieve high-reduction pressing in a single pass. In other words, with this conventional plate reduction press apparatus, the material to be pressed is transferred in the downstream direction of the transfer line together with the dies 34 when the dies are pressing the material 31 to be reduced, but when the dies are separated from the material, feeding stops, and as a result, the material to be pressed is fed intermittently, not continuously.
Although the speed of feeding the material can be adjusted intermittently by changing the frequency of the pressing cycles, it is difficult to adjust the speed in synchronism with a downstream finish rolling mill etc., continuously and precisely, because of the intrinsic structure of the plate reduction press apparatus, and even if such an adjustment can be achieved, the required pressing frequency and pressing loads (pressing forces) become excessively large when only the pressing frequency is used for the adjustment, which has given rise to problems such as large vibrations and a remarkable reduction in the life of the equipment.
6. FIG. 4 shows an example of a rough rolling mill used for hot rolling, which is provided with work rolls 42a, 42b arranged opposite each other above and below a transfer line S on which a plate-like material 41 to be shaped is passed substantially horizontally, and backup rolls 43a, 43b in contact with the work rolls 42a, 42b, respectively, on the opposite side from the transfer line.
In the aforementioned rough rolling mill, the work roll 42a above the transfer line S is rotated counterclockwise, and the work roll 42b below the transfer line S is rotated clockwise, while the material 41 to be shaped is inserted between both work rolls 42a, 42b, and at the same time, the upper backup roll 43a is pressed downwards, and while the material 41 to be shaped is moved from the upstream A side of the transfer line to the downstream B side of the transfer line, the material 41 to be shaped is reduced and formed in the direction of the plate thickness. However, unless the nip angle of the work rolls 42a, 42b with respect to the material 41 to be shaped is less than about 17xc2x0, slipping takes place between the upper and lower surfaces of the material 41 and the outer peripheries of both work rolls 42a, 42b, and the work rolls 42a, 42b can no longer grip the material 41 to be shaped.
Therefore, when the diameter D of the work rolls 42a, 43b is 1,200 mm, the amount of the reduction T per pass becomes about 50 mm according to the above-mentioned condition of the nip angle of the work rolls 42a, 42b, so when a material 41 with a plate thickness T0 of 250 mm is reduced, and formed by the rough rolling mill, the plate thickness T1 after pressing is about 200 mm.
Consequently, a plurality of rough rolling mills are arranged conventionally, or the plate thickness is reduced sequentially as the material 41 to be shaped is moved backwards and forwards, through one rolling mill, which is called reverse rolling, and after the plate thickness of the material 41 being shaped is reduced to about 90 mm, the material 41 being shaped is transferred to a finish rolling mill.
However, when reverse rolling such as described above is carried out, space for pulling out the material 41 to be or being shaped must be prepared on both the upstream A and downstream B sides of the transfer line in a group of rolling mills, therefore the equipment becomes so long and large that the material 41 to be shaped cannot be efficiently reduced in plate thickness, which imposes a practical problem.
In addition, if the material to be shaped is passed through the rough rolling mills many times, the temperature of the material 41 to be shaped decreases, so the material 41 being shaped must be reheated before finish rolling.
7. Another type of high-reduction press system capable of reducing the thickness of a slab to about one half in a single pass has also been developed. FIG. 5 shows the shapes of a slab 51 when its thickness is highly reduced by such a high-reduction press system or mill. View (A) shows the state before pressing the slab 51 with dies or rolls 61, and (B) shows the shape of the slab 51 after its thickness has been reduced to nearly one half. Before and after pressing, the volume of the slab remain substantially the same so when the thickness is reduced to one half, approximately, the volume of the other remaining one half must spread in the longitudinal and lateral directions of the slab 51. The volume pressed out in the lateral direction produces bulges 62 at both edges.
FIG. 6 shows edge cracks 63 created in the bulges 62. The surface of a bulge 62 is often stressed because the surface is cooled, and edge cracks 63 are produced frequently. FIG. 7 illustrates the conditions when a highly reduced slab 51 is rolled in a downstream rolling mill. (A) and (B) show the state immediately before rolling with the rolls 64 and seam flaws 66 have appeared on the surface of the rolled material. The portion at the peak 65 of a bulge 62 is cooled early, so the edge cracks shown in FIG. 6 often appear, and even if there are no apparent cracks, the surface is liable to have cracks, and when the material is rolled, longitudinal flaws are produced after rolling. These are called seam flaws. These edge cracks and seam flaws are not desirable because they sometimes remain in the product. Also when a slab 801 is highly reduced by means of dies 804 with inclined surfaces 804b in the longitudinal direction of the slab as shown in FIG. 34, there is the problem that slipping may often occur between the slab 801 and the dies, so that the slab cannot be reduced satisfactorily.
8. On the other hand, according to the prior art, a sizing press and a roughing mill are used to reduce the width and thickness of a slab, respectively. In this case, the slab to be reduced is as short as 5 m to 12 m, and after the slab has been pressed with a sizing press to a uniform width over the entire length of the slab, the thickness is then reduced with a roughing mill. The slab is moved backwards and forwards through sizing press and the roughing mill while pressing and rolling the slab to obtain the predetermined width and thickness, in a reversing pressing and rolling process.
However, since a long slab has been introduced following the development of the continuous casting system, reversing pressing with a sizing press or rolling with a roughing mill cannot be applied to a long slab. Another problem is that when a slab is pressed and rolled simultaneously using a sizing press and a roughing mill, the operations of the sizing press and the roughing mill adversely affect each other.
1. The present invention was aimed at solving the various problems described above. That is, the first object of the present invention is to provide a hot rolled steel sheet manufacturing apparatus that can manufacture a hot rolled steel sheet from a hot rolled long slab in which a plurality of steel sheet coils are manufactured continuously (that is, xe2x80x9clong slabxe2x80x9d means a slab with a length such that a hot rolled steel sheet is produced with a length corresponding to that of a plurality of hot rolled steel coils each of which has a normal length,xe2x80x9d throughout this specification), can reduce the loss of heat from the hot slab during the manufacture of the hot rolled steel sheet, with a high quality free from internal defects etc., with a high production efficiency and a high yield, and a method of manufacturing the hot rolled steel sheet using this apparatus.
To achieve the first object of the present invention, according to the first preferred embodiment of the present invention, the hot rolled steel sheet manufacturing apparatus is provided with continuous casting facilities for continuously casting a hot slab, rough processing facilities for processing the hot slab cast by the aforementioned continuous casting facilities and forming the slab into a sheet bar, a group of finish rolling mills that roll the sheet bar manufactured by the above-mentioned rough processing facilities, and a coiler that reels the hot rolled steel sheet, which are located in that order, a hot rolled steel sheet manufacturing apparatus, in which the aforementioned rough processing facilities are provided with a casting means at least as a part of the thickness reducing and processing means, and a cutting means that cuts a hot rolled steel sheet while moving between the above-mentioned group of finish rolling mills and the coiler, and is arranged between them.
According to the second preferred embodiment, the hot rolled steel sheet manufacturing apparatus according to the first preferred embodiment is provided with rough processing facilities located closer to the group of finish rolling mills than the mid-point between the outlet of the continuous casting facilities and the inlet of the group of finish rolling mills.
According to the third preferred embodiment, using the hot rolled steel sheet manufacturing apparatus according to the first two preferred embodiments, a heating furnace is installed that can supply the rough processing facilities with a reheated slab in addition to the system comprised of the continuous casting facilities, rough processing facilities, group of finish rolling mills and the coiler.
Further according to the fourth preferred embodiments, using the hot rolled steel sheet manufacturing apparatus according to any one of the three previous embodiments, means for heating and holding and/or heating a material to be processed are arranged at one location or two or more locations either inside the rough processing facilities, between the continuous casting facilities and the rough processing facilities, inside the rough processing facilities, or between the rough processing facilities and the group of finish rolling mills.
Also according to the fifth preferred embodiment, in the method of manufacturing a hot rolled steel sheet using the hot rolled steel sheet manufacturing apparatus according to any one of the previous four embodiments, a hot rolled steel sheet is manufactured from a long, hot rolled slab with a thickness of 100 mm or more and with a length corresponding to the length of a plurality of coils of hot rolled steel sheets, which is cast in a continuous casting facility, and the aforementioned long, hot rolled slab is processed into a sheet bar, by transferring the slab to the rough processing facilities where the slab produced at least by the casting means is reduced and processed with a large reduction ratio, and in continuation, the above-mentioned sheet bar is rolled by the group of finish rolling mills, into a hot rolled steel sheet with a predetermined thickness, and then the hot rolled steel sheet is reeled onto a coiler, and when so required, the sheet is cut while the steel sheet is moving, thus the hot rolled steel sheet is manufactured as a coil with a predetermined length.
The sixth preferred embodiment is the method of manufacturing a hot rolled steel sheet according to the sixth preferred embodiment, in which at the outlet of the continuous casting facilities, a hot slab is cut into long slabs the length of each of which corresponds to the length of a plurality of hot rolled steel sheets, and the above-mentioned long slabs are supplied to the rough processing facilities.
The seventh preferred embodiment, using the hot rolled steel sheet manufacturing apparatus specified in the third or fourth preferred embodiments, a reheated slab with a normal length, taken from the heating furnace is supplied to the rough processing facilities, during the period between the time that the rough processing facilities complete the reducing and processing of a long, slab supplied from the continuous casting facilities and the time that the next long, hot slab is supplied from the continuous casting facilities, and the reheated slab is reduced and processed by the rough processing facilities and is rolled by the group of finish rolling mills, thereby manufacturing a hot rolled steel sheet.
Also according to the eighth preferred embodiment, a hot rolled steel sheet manufacturing apparatus is provided with rough processing facilities that reduce and process a hot slab into a sheet bar, and a group of finish rolling mills that roll the sheet bar manufactured in the aforementioned processing facilities, into a hot rolled steel sheet with a predetermined thickness, in which the above-mentioned rough processing facilities are composed of a casting and processing means at least as a part of the thickness reducing and processing means.
The ninth preferred embodiment discloses a method of manufacturing a hot rolled steel sheet, using the hot rolled steel sheet manufacturing apparatus of the eighth preferred embodiment, in which a hot slab with a thickness of 100 mm or more is reduced and processed into a sheet bar by the rough processing facilities, in which the hot slab is forged and processed at least with a forging reduction ratio of 30% or more per pass of reduction and forming, using forging and processing means, and in continuation the aforementioned sheet bar is rolled by the group of finish rolling mills into a hot rolled steel sheet with a predetermined thickness.
2. The second object of the present invention is to provide a method of manufacturing a hot rolled steel sheet and the apparatus concerned which has the advantages that (1) a plate reduction press apparatus is used in place of a rough rolling mill, thereby the length of the rolling line can be reduced and the cost of the whole equipment can be reduced greatly, (2) because a press machine can reduce the thickness of a slab with a medium thickness of 50 mm to 150 mm to about 20 mm, and the slab with a thickness of 20 mm can be maintained at a high temperature, a press machine and a finish rolling mill can be operated continuously (in tandem), (3) since a slab with a length that can be reeled into one coil in a batch system is supplied, and is highly reduced and can then be rolled, a shear machine with a complicated structure, located immediately before the coiler, can be omitted and the rolling line can be shortened, (4) because the plate reduction press apparatus is used, high temperature material does not have to be worked backwards and forwards, and can be conveyed to a finish rolling mill, therefore an intermediate coiler or a coil box can be eliminated thereby shortening the rolling line, and a high yield of the material being rolled can be achieved, (5) the use of the plate reduction press apparatus means that the temperature for heating the slab can be lower, therefore the energy consumption can be reduced, and (6) very thinly rolled material can be manufactured.
To achieve the second object of the present invention, a method of manufacturing a hot rolled steel sheet is provided, in which a continuous casting machine manufactures a slab with a thickness of 50 to 150 mm, next the slab is heated to and maintained at a predetermined temperature while the slab is being conveyed on a press line, by means of a slab heating and holding furnace, then the slab is highly reduced to a predetermined thickness by a plate reduction press machine as the slab is being taken from the slab heating and holding furnace, to produce a pressed material, and next the pressed material is rolled continuously by a plurality of finish rolling mills as the pressed material is being transferred from the plate reduction press machine, to produce a steel sheet with a predetermined thickness, and thereafter the steel sheet is cut into predetermined lengths and reeled onto a coiler.
According to the method of the tenth preferred embodiment of the present invention, (1) a continuous casting machine manufactures a slab with a thickness of 50 mm to 150 mm, (2) next the slab is heated to and maintained at a predetermined temperature while the slab is being conveyed to a press machine, by means of a slab heating and holding furnace, (3) then the slab is highly reduced to a predetermined thickness (about 20 mm) by a plate reduction press machine while the slab is being transferred from the slab heating and holding furnace, and next (4) the pressed material is rolled continuously by a plurality of finish rolling mills while the pressed material is transferred from the plate reduction press machine to produce a steel sheet with a predetermined thickness (0.8 to 12.0 mm), and then (5) the steel sheet is cut into predetermined lengths and reeled onto a coiler.
Therefore, because a slab manufactured by the continuous casting machine that has cooled to some extent during conveying on the rolling line, can be heated to and maintained at a predetermined temperature by the slab heating and holding furnace, the slab can be pressed and formed easily and quickly by the plate reduction press apparatus on the downstream side. In addition, because a slab with a length of about 20 m, is pressed and formed by the plate reduction press apparatus instead of a plurality of rough rolling mills used in the prior art before being conveyed to the finish rolling mills, the slab can be pressed and formed quickly in a good condition with a smaller temperature decrease than in the prior art. Furthermore, the pressed material can be transferred continuously (in tandem) at a high temperature to the finish rolling mills, so a very thin sheet of 0.8 to 1.0 mm can be manufactured.
According to the eleventh preferred embodiment of the present invention, a hot rolled steel sheet manufacturing apparatus is provided with a continuous casting machine for manufacturing a slab with a thickness of 50 mm to 150 mm, a slab heating and holding furnace that heats the slab, as the slab is being conveyed on a press line, and holds the slab at a predetermined temperature, a plate reduction press machine that presses the slab, as the slab is being transferred from the slab heating and holding furnace, by a large amount of reduction into a pressed material with a predetermined thickness, a plurality of finish rolling mills that continuously roll the pressed material as the material is being transferred from the plate reduction press machine, a shear machine that cuts the material that has been pressed into predetermined lengths, and a coiler that reels the material being cut.
In the configuration of the eleventh preferred embodiment according to the present invention, a plate reduction press apparatus highly reduces a medium-thickness slab in the direction of the plate thickness as the slab is continuously supplied from the continuous casting facilities, thereby eliminating the plurality of rough rolling mills for the rough rolling process and an intermediate coiler for heating and holding the slab, conventionally used in the prior art, therefore the rolling line can be shortened and the cost of the equipment can be reduced. In addition, a slab can be conveyed continuously from the continuous casting machine, so that coils can be mass produced very efficiently, and the productivity of the material being rolled can be increased.
According to the twelfth preferred embodiment, the aforementioned slab heating and holding furnace is composed of a tunnel furnace or a double walking beam furnace, together with a looper for delaying the slab before and after the plate reduction press machine. Also according to the thirteenth preferred embodiment, the hot rolled steel sheet manufacturing apparatus is provided with a stentering press machine or a vertical rolling mill that presses the slab in the lateral direction thereof, located before the plate reduction press machine, and/or a vertical rolling mill that presses the slab in the lateral direction thereof, located at the inlet of the finish rolling mills.
In this configuration, a slab manufactured by the continuous casting machine and cooled during transportation on the rolling line, can be quickly and easily heated to and maintained at a predetermined optimum temperature, thanks to induction heating or gas heating tools provided on the ceiling or side surfaces of the tunnel furnace. In addition, any excess (or deficit) of the slab, caused by a difference in the pressing speeds of the plate reduction press apparatus and the finish rolling mills, can be accommodated by the looper, so the excess (or deficit) can be evened out. Moreover, a change or constraint in the lateral dimensions of the slab can be produced speedily and easily because the slab can be pressed before being transferred to the plate reduction press apparatus, by using the lateral pressing dies of the stentering press machine or the vertical rolls of the vertical rolling mill. In addition, because a vertical rolling mill is located at the inlet of the finish rolling mills, variations in the width of the slab, produced in the press apparatus, can be corrected so that the material being rolled will have a high-quality flat shape.
According to the fourteenth preferred embodiment, a shear machine is also provided and is located between the aforementioned continuous casting machine and the tunnel furnace, and cuts the slab when so required. In this configuration, a shear machine is located between the continuous casting machine and the tunnel furnace, so that when a slab which is normally conveyed continuously and efficiently, must be stopped from being transferred to the rolling line because of some operational reason, or when a slab is to be manufactured for several coils or one coil, the slab can be cut quickly. The fifteenth preferred embodiment provides a hot rolled steel sheet manufacturing apparatus with a tunnel furnace located at the inlet of the finish rolling mills, that heats the slab and maintains the slab at a predetermined temperature. In this configuration, because the tunnel furnace with the same heating and holding mechanisms as described above is located at the inlet of the finish rolling mills, the tunnel furnace heats the slab and maintains it at a predetermined temperature to compensate for the temperature drop that is expected to occur when the slab is held up in the looper, therefore the slab can be conveyed to the finish rolling mills at an optimum temperature.
The hot rolled steel sheet manufacturing apparatus according to the sixteenth preferred embodiment of the present invention is provided with a line A composed of any or all of the apparatus and methods embodiments tenth through the fifteenth, a line B comprised of a second continuous casting machine and a second heating furnace (tunnel furnace or walking beam furnace), and a second slab heating and holding furnace that transfers a slab on line B to line A, in which the second slab heating and holding furnace can transfer slabs corresponding to one coil or a plurality of coils.
The seventeenth preferred embodiment of the present invention relates to a method of manufacturing hot rolled steel sheet using only the line A specified in the sixteenth preferred embodiment; a. the material is continuous from the continuous casting facilities to the coiler, and several coils are manufactured with the sheet being cut before the coiler, and/or b. a slab corresponding to several coils is cut by a cutting machine at the outlet of the continuous casting facilities, continuously rolled, and the coils are produced by cutting the rolled sheet before the coiler, and/or c. a slab corresponding to one coil is cut by the cutter at the outlet of the continuous casting facilities, and each coil is rolled and reeled individually.
The eighteenth preferred embodiment of the present invention discloses a method of manufacturing hot rolled steel sheet using the lines A and B, according to the sixteenth preferred embodiment, in which the line A is configured with a, b and c of the seventeenth preferred embodiment, the line B is configured with b and c of the seventeenth preferred embodiment, and is combined with the line A, and slabs taken from the lines A and B are rolled alternately.
According to the nineteenth preferred embodiment of the present invention, a method of manufacturing hot rolled steel sheet is offered, in which a slab with a plate thickness of about 50 mm to 150 mm is manufactured by a continuous casting machine, next the slab is cut into predetermined lengths each of which can be reeled into one coil of rolled material, by a shear machine, then the slab is heated to and maintained at a predetermined temperature by a slab heating and holding furnace, while the slab is being conveyed on a rolling line, next the slab is pressed by a large amount and reduced to a pressed material with a predetermined thickness by a plate reduction press machine, while the slab is being conveyed from the slab heating and holding furnace, then the pressed material is rolled to the thickness of the product continuously by a plurality of finish rolling mills, as the pressed material is conveyed from the plate reduction press machine, and the material after being rolled to the thickness of the product is reeled into a coil, as the material is rolled coil by coil.
The process of the method according to the nineteenth preferred embodiment described above can be broken down into (1) the continuous casting machine manufactures a slab with a thickness of about 50 mm to 150 mm, (2) next the shear machine cuts the slab to predetermined lengths each of which after the material has been rolled can be reeled into one coil, (3) then while the slab is conveyed on the rolling line, the slab is heated to and maintained at a predetermined temperature by the slab heating and holding furnace, (4) the slab is reduced by a large amount to a predetermined thickness (about 20 mm) by the plate reduction press apparatus while the slab is being conveyed from the slab heating and holding furnace, (5) then while the slab is being transferred from the plate reduction press apparatus, the pressed material is rolled continuously by a plurality of finish rolling mills to the thickness of the product (about 0.8 to 1.0 mm), and (6) the material after being rolled is reeled coil by coil as it is being rolled.
Therefore, because the slab manufactured by the continuous casting machine and cut to a length corresponding to one coil is heated to and maintained at a predetermined temperature by the slab heating and holding furnace, and the slab can be conveyed to the plate reduction press apparatus in this state, the reducing and forming operations can be carried out easily and quickly. In addition, since a plate with a thickness of about 20 mm is reduced and formed by the plate reduction press apparatus, instead of a plurality of rough rolling mills according to the prior art, consequently the temperature of the slab is less than that used in conventional methods, and high-quality forming and reducing operations can be completed quickly. Furthermore, the pressed material can be conveyed continuously (in tandem) and quickly at a high temperature to the finish rolling mills, so that a very thin rolled material of about 0.8 to 1.0 mm can be produced. Also, the rolling line can be shortened by using the plate reduction press apparatus and batch operation in which one slab corresponds to one coil.
The twentieth preferred embodiment of the present invention discloses a hot rolled steel sheet manufacturing. apparatus provided with a continuous casting machine for manufacturing a slab with a thickness of about 50 mm to 150 mm, a shear machine located at the outlet of the continuous casting machine, for cutting the slab to a predetermined length from which material after being rolled can be reeled into one coil, a slab heating and holding furnace for heating the slab and holding it at a predetermined temperature as the slab is being conveyed on the rolling line, a plate reduction press machine for pressing the slab by a large amount as the slab is conveyed from the slab heating and holding furnace, to a predetermined thickness, a plurality of finish rolling mills for continuously rolling the material after being pressed by and conveyed from the plate reduction press machine, to a rolled material with the thickness of the product, and a coiler for reeling the rolled material as the material for one coil is conveyed from the finish rolling mills.
In the configuration of the twentieth preferred embodiment, the plate reduction press apparatus reduces a medium-thickness slab by a large amount in the direction of the plate thickness, that has been produced by the continuous casting facilities, in a batch system for a plurality of coils, instead of a plurality of rough rolling mills conventionally used for rough rolling and so eliminating the intermediate coiler also used in the prior art for heating and holding a slab, therefore the rolling line can be shortened and the cost of the equipment can be reduced. In addition, the use of the plate reduction press apparatus enables a slab with a thickness of about 20 mm to be conveyed to the finish rolling mills at a high temperature, so that the amount of heat used for heating the slab can be reduced, thus conserving energy.
In the twenty-first preferred embodiment, the aforementioned slab heating and holding furnace is a tunnel furnace or a double walking beam furnace and a looper for holding up a slack portion of the slab is provided between the plate reduction press machine and the finish rolling mills. According to the twenty-second preferred embodiment, the hot rolled steel sheet manufacturing apparatus is provided with a stentering press machine or a first vertical rolling mill located on the upstream side of the plate reduction press machine, for rolling the slab in the lateral direction thereof, and/or a second vertical rolling mill located at the inlet of the finish rolling mills, for rolling the slab in the lateral direction thereof.
In this configuration, an induction heating or gas heating system is provided on the ceiling or side surface of the tunnel furnace to heat the slab and maintain the temperature thereof, and the slabs manufactured by the continuous casting machine and cut into lengths corresponding to individual coils can be quickly and easily heated to and maintained at a predetermined optimum temperature. In addition, an excess (or deficit) portion of the slab, produced by a difference between the reducing speeds of the plate reduction press machine and the finish rolling mills is held up in the looper, so that the excess (or deficit) length can be evened out. Furthermore, the slab can be pressed in the lateral direction thereof by means of the lateral pressing dies of the stentering press machine or the vertical rolls of the vertical rolling mill, before being transferred to the plate reduction press apparatus, so the lateral dimensions of the slab can be changed or constrained quickly and easily. Also, since the vertical rolling mill is located at the inlet of the finish rolling mills, any variations in the lateral dimensions, produced by pressing, can be corrected, and a rolled material with a good shape can be produced.
The hot rolled steel sheet manufacturing apparatus according to the twenty-third preferred embodiment of the present invention is provided with a line A according to any or all of claims 19 through 22, a line B comprised of a second continuous casting machine and a second heating furnace (tunnel furnace or walking beam furnace), which is located alongside the casting machine and the heating furnace of line A, and a second heating and holding furnace for transferring a slab in line B to line A, in which the aforementioned second heating and holding furnace can transfer slabs corresponding to one coil. Also, the method of manufacturing a hot rolled steel sheet specified in the twenty-fourth preferred embodiment relates to the case in which the line A and the line B according to the twenty-third preferred embodiment are installed, and each slab corresponding to one coil, output from the lines A and B, in sequence is pressed with a high reduction ratio, into a pressed material, and then the pressed material is rolled coil by coil, and the rolled material is reeled into one coil.
Therefore, according to the aforementioned casting apparatus and methods, the production efficiency can be improved because slabs can be supplied alternately, from the continuous casting facilities, to the rolling line in a batch system in an efficient manner.
In the twenty-fifth preferred embodiment of the present invention, a hot rolled steel sheet manufacturing apparatus is provided with a rolling line comprised of a stentering press machine or a first vertical rolling mill for pressing or rolling a slab in the lateral direction thereof, downstream from a slab heating and holding furnace, a plate reduction press apparatus for pressing the slab with a high reduction ratio, to a predetermined thickness, a looper for holding up a slack portion of the slab, a second vertical rolling mill located at the inlet of the finish rolling mill, for pressing the slab in the lateral direction thereof, into a pressed material, a plurality of finish rolling mills for rolling the pressed material continuously to a rolled material with the thickness of the product, and a coiler for reeling the rolled material, corresponding to one coil, in which a plurality of continuous casting machines located on the upstream side of the aforementioned slab heating and holding furnace in the rolling line, opposite each other for manufacturing slabs with a thickness of about 50 mm to 150 mm, a shear machine located at the outlet of the continuous casting machines for cutting the slabs into lengths corresponding to the length of rolled material to be rolled into one coil, and heating furnaces of the walking beam type are installed. According to twenty-sixth preferred embodiment, when the hot rolled steel sheet manufacturing apparatus of the twenty-fifth preferred embodiment is provided with a plurality of walking beam type heating furnaces, a hot rolled steel sheet is manufactured by the method in which slabs are transferred from the walking beam type heating furnaces in sequence to the rolling line, pressed with a high reduction ratio into pressed material, then the material is rolled into rolled material, coil by coil, and the rolled material for one coil is reeled into a coil.
Consequently, the casting facilities and the methods according to the present invention can also improve the productivity of the rolled material, because medium-thickness slabs manufactured by a plurality (for instance, 2 machines) of continuous casting machines and cut so that they can be reeled by the coiler into one coil, in a batch system, can be supplied efficiently into the rolling line.
3. The third object of the present invention is to provide an apparatus capable of hot pressing and rolling both a slab of a normal length and a long slab. In addition, the object also includes presenting an apparatus that manufactures coils of thin sheets with different widths and/or thicknesses, from a long slab.
To achieve the third object described above, the twenty-seventh preferred embodiment provides a hot rolled steel sheet manufacturing apparatus with a heating furnace for heating a slab supplied from upstream, at least one first roughing mill located on the downstream side of the heating furnace, a plate reduction press apparatus located on the downstream side of the first roughing mill, at least one second roughing mill located on the downstream side of the plate reduction press apparatus, a plurality of finish rolling mills located on the downstream side of the second roughing mill, a flying shear machine located on the downstream side of the plurality of finish rolling mills, and a coiler located on the downstream side of the flying shear machine.
With this apparatus, a slab with a normal length is processed by the heating furnace, first roughing mill and second roughing mill, finish rolling mills, and coiler. For a long slab, the heating furnace is not used because the slab has been heated before entering the pressing line, therefore the plate reduction press apparatus or the plate reduction press apparatus and second roughing mill, or the first roughing mill and plate reduction press apparatus and second roughing mill, and finish rolling mills, flying shear machine and coiler are used.
In the invention of the twenty-eighth preferred embodiment using the hot rolled steel sheet manufacturing apparatus specified in the twenty-seventh preferred embodiment, a slab with a normal length is heated by the aforementioned heating furnace, rough rolled by the first roughing mill or the plate reduction press apparatus, rough rolled by the second roughing mill, finish rolled by the finish rolling mills, and reeled by the coiler. A long slab is rough pressed or rolled by the plate reduction press apparatus, or the plate reduction press apparatus and the second roughing mill, or the first roughing mill, the plate reduction press apparatus and the second roughing mill, then finish rolled by the finish rolling mills, cut by the flying shear machine into predetermined lengths, and reeled by the coiler.
When the first roughing mill is used for a slab with a normal length, reverse rolling is also applied normally, and the slab is rolled in a plurality of passes. With the plate reduction press apparatus, the slab is reduced in one pass. For a long slab, the means of rough rolling is selected from the plate reduction press apparatus, or the plate reduction press apparatus and the second roughing mill, or the first roughing mill, the plate reduction press apparatus and the second roughing mill, depending on what plate thickness is to be achieved by the rough rolling. In addition, the rolled material cannot be reeled into one coil, therefore the flying shear machine is used so that the material can be reeled into a plurality of coils.
In the twenty-ninth preferred embodiment of the invention, a stentering press is located between the aforementioned heating furnace and the above-mentioned first roughing mill. Using such a stentering press machine, coils of thin steel sheets with different widths can be manufactured.
In the thirtieth preferred embodiment of the invention, thin steel sheets with different widths and/or thicknesses are pressed or rolled by the stentering press machine and the plate reduction press apparatus, or the plate reduction press apparatus and the second roughing mill, or the first roughing mill, the plate reduction press apparatus and the second roughing mill, and the finish rolling mills, and then each type of very thin steel sheets with different widths and thicknesses is reeled by the coiler and cut by the flying shear machine.
If a finished very thin steel sheet cannot be reeled into one coil, it must be divided into a plurality of coils each of which is reeled separately. Therefore, it is possible to classify each combination of widths and thicknesses of very thin steel sheet, coil by coil, when rolling the sheet. The stentering press machine presses the width of a slab, to the required width for each coil to be reeled. In addition, a length of the slab corresponding to each width, is pressed and rolled so that the very thin sheets reeled into coils can be classified according to the required thicknesses and widths, using the plate reduction press apparatus, or the plate reduction press apparatus and the second roughing mill, or the first roughing mill, the plate reduction press apparatus and the second roughing mill. Thus, a plurality of coils with different widths and thicknesses can be manufactured from a slab.
4. The fourth object of the present invention is to present a hot rolled steel sheet manufacturing apparatus in which a material to be pressed or rolled can be moved substantially continuously in synchronism with finish rolling mills etc. located on the downstream side of a production line, without having to make fine adjustments to the frequency of the pressing cycles.
According to the thirty-first preferred embodiment of the invention established to achieve the fourth object, a hot rolled steel sheet manufacturing apparatus is composed of a plate reduction press apparatus constructed so that the dies can move in the downstream direction of a pressing line for a material to be pressed, while the material is being pressed by the dies, and a feeding device that moves the aforementioned material to be pressed in the downstream direction, in which while the dies of the plate reduction press apparatus are not in contact with the material to be pressed, or when the dies are pressing the material to be pressed or not in contact therewith, the feeding device moves the material to be rolled in the downstream direction.
In the configuration of the thirty-first embodiment described above, the plate reduction press apparatus moves the material to be pressed in the downstream direction of the pressing line while the material is being pressed by the dies, and in addition, the feeding device also moves the material to be pressed in the downstream direction even when the dies are not in contact with the material, therefore by adjusting the feeding speed of the device, the material to be rolled can be moved substantially continuously, in synchronism with the finish rolling mills etc. located on the downstream side without having to make fine adjustments to the frequency of the pressing cycles.
In the thirty-second preferred embodiment of the invention, the aforementioned plate reduction press apparatus is provided with pressing mechanisms that move the dies eccentrically in a circular path with a radius of r, the dies come in contact with the material to be pressed when the angle of rotation from the upstream horizontal line to the material to be pressed has a positive value the dies press the material and move while pressing, the speed at which the dies move reaches a maximum V when=90xc2x0, the above-mentioned feeding device feeds the material to be pressed at a speed v=Vsin when the dies are pressing, and feeds the material to be pressed substantially at a constant speed v0 during the period when the material is not being pressed, and the aforementioned constant speed v0 can be varied.
In this configuration, the feeding device feeds the material to be pressed at a speed v=Vsin when the dies are pressing, so slipping of the material to be pressed relative to the means of feeding (for instance, conveyor rollers) can be prevented, thus preventing energy losses, scratches, etc. due to slipping. In addition, the material to be roiled is fed substantially at a constant speed v0 during then period when the material is not being pressed, and because this speed is variable, the speed is adjusted so that the material to be rolled can be moved substantially continuously, in synchronism with the finish rolling mills etc. located on the downstream side without having to make fine adjustments to the frequency of the pressing cycles.
The thirty-third preferred embodiment of the present invention provides a hot rolled steel sheet manufacturing apparatus with a plate reduction press apparatus that moves a material to be pressed in the downstream direction of a pressing line while the material is being pressed by the dies, a feeding device for moving the material to be pressed in the downstream direction, a rolling mill located on the downstream side of the plate reduction press apparatus, that continuously presses the material to be rolled, and a looper device located between the plate reduction press apparatus and the rolling mill, that accommodates a slack portion of the material to be rolled, produced therebetween, in which the mean feeding speed vs at the inlet of the plate reduction press apparatus is set to be identical to the mass flow of the material to be rolled on the downstream side of the rolling mill, and the feeding speed v0 of the feeding device during the period when the material is not being pressed is set such that the mean feeding speed during a pressing cycle agrees with the aforementioned speed vs.
In this configuration, the mean feeding speed vs at the inlet of the plate reduction press apparatus is set to be identical to the mass flow of the material being rolled on the downstream side of the rolling mill, and the feeding speed v0 of the feeding device during the period when the material is not being pressed is set such that a mean feeding speed during a pressing cycle agrees with the aforementioned speed, therefore the maximum amount of slack produced in the material to be rolled, between the plate reduction press apparatus and the rolling mill, is only that due to the differences in the feeding speed during a pressing cycle, so the looper device can be made compact.
5. The fifth object of the present invention is to provide a hot rolled steel sheet manufacturing apparatus that can efficiently press, roll and form a material to be shaped in the direction of the plate thickness, and a method of manufacturing a hot rolled steel sheet.
In the method of manufacturing a hot rolled steel sheet, described in the thirty-fourth preferred embodiment of the present invention, with the aim of achieving the fifth object, dies are moved towards and away from each other on both sides of a material to be shaped, heated to a predetermined temperature, and press and form the aforementioned material in the direction of the plate thickness of the material, a portion of the material after being shaped by the dies is inserted between the upper and lower work rolls and rolled and formed therebetween, and a slack portion is produced in the pressed material between the dies and the above-mentioned work rolls located in the close vicinity of the dies.
According to the method of manufacturing a hot rolled steel sheet specified in the thirty-fifth preferred embodiment of the present invention, first dies are moved towards and away from each other in the left and right directions of a material to be shaped, and press and form the material in the direction of the plate width, the portion of the material that has been shaped by the first dies is heated to a predetermined temperature, second dies are moved towards and away from each other in the up and down direction of the material to be shaped, and press and form the material in the direction of the plate thickness, the portion of the material after being shaped by the second dies is inserted between the upper and lower work rolls, and rolled and formed, and an appropriate slack portion is produced in the material being shaped between the second dies and the work rolls located close to the aforementioned second dies.
In the method of manufacturing a hot rolled steel sheet specified in the thirty-sixth preferred embodiment of the present invention, first dies are moved towards and away from each other on the left and right sides of a material to be shaped, heated to a predetermined temperature, and press and form the material in the direction of the plate width, second dies are moved towards and away from each other in the up and down direction of the portion of the material, that has been pressed by the first dies in the left and right direction of the material, and press and form the material in the direction of the plate thickness, the portion of the material, that has been pressed by the second dies is next inserted between the upper and lower work rolls, and rolled and formed, and a slack portion of the material being shaped is formed by an appropriate deflection downwards between the second dies and the work rolls located close to the aforementioned second dies.
According to the method of manufacturing a hot rolled steel sheet specified in the thirty-seventh preferred embodiment of the invention, in addition to the means for manufacturing a hot rolled steel sheet, specified in either the thirty-fifth or the thirty-sixth embodiments of the present invention, a slack portion of the material to be shaped is formed by an appropriate deflection downwards between the dies for press forming in the lateral direction and the dies for press forming in the direction of the plate thickness.
The hot rolled steel sheet manufacturing apparatus specified in the thirty-eighth preferred embodiment of the present invention is provided with a tunnel furnace that can heat the material to be shaped which is moving on a transfer line, a plate reduction press machine with a pair of upper and lower dies that can move towards and away from each other in the up and down direction of the transfer line, in synchronism with each other and are located on the downstream side of the aforementioned tunnel furnace on the transfer line, a plurality of roughing mills each of which is comprised of a pair of upper and lower work rolls located opposite each other above and below the transfer line and are located in series on the downstream side of the above-mentioned plate reduction press machine on the transfer line, and a looper mechanism that is located between the plate reduction press machine and the first roughing mill in the upstream direction of the transfer line and can form a slack portion of the material to be shaped in a downward deflection, when the material is moving on the transfer line.
In the hot rolled steel sheet manufacturing apparatus specified in the thirty-ninth preferred embodiment of the invention, there is a stentering press machine with a pair of left and right dies that can move towards and away from a transfer line on the left and right sides of the transfer line in synchronism with each other, a tunnel furnace that can heat the material to be shaped, which is moving on the transfer line and is located on the downstream side of the aforementioned plate reduction press machine on the transfer line, a plate reduction press machine with a pair of upper and lower dies that can move towards and away from the transfer line in the up and down direction of the transfer line and is located on the downstream side of the above-mentioned tunnel furnace on the transfer line, a plurality of roughing mills each of which is comprised of a pair of upper and lower work rolls located opposite each other above and below the transfer line and are located in series on the downstream side of the aforementioned plate reduction press machine on the transfer line, and a looper mechanism that is located between the plate reduction press machine and the first roughing mill in the upstream direction of the transfer line and can form a slack portion of the material to be shaped in a downward deflection, when the material is moving on the transfer line.
The hot rolled steel sheet manufacturing apparatus described in the fortieth preferred embodiment of the present invention is composed of a tunnel furnace that can heat a material to be shaped, which is moving on a transfer line, a stentering press machine with a pair of left and right dies that can move towards and away from the transfer line on the left and right sides of the transfer line, in synchronism with each other, and is located on the downstream side of the above-mentioned tunnel furnace on the transfer line, a plate reduction press machine with a pair of upper and lower dies that can move towards and away from the transfer line in the up and down direction of the transfer line and is located on the downstream side of the aforementioned stentering press machine on the transfer line, a plurality of roughing mills each of which is comprised of a pair of upper and lower work rolls located opposite each other above and below the transfer line, and are located in series on the downstream side of the above-mentioned plate reduction press machine on the transfer line, and a looper mechanism that is located between the late reduction press machine and the first roughing mill in the upstream direction of the transfer line and can form a slack p portion of the material to be shaped in a downward deflection, when the material is moving on the transfer line.
In the hot rolled steel sheet manufacturing apparatus specified in the forty-first preferred embodiment of the present invention, in addition to the means described in claim 39, a second looper mechanism is located between the stentering press machine and the tunnel furnace or between the tunnel furnace and the plate reduction press machine, and can form a slack portion of the material to be shaped in a downward deflection, when the material is moving on the transfer line.
The hot rolled steel sheet manufacturing apparatus specified in the forty-second preferred embodiment of the present invention, which in addition to including the configuration of components of the hot rolled steel sheet manufacturing apparatus mentioned in the fortieth preferred embodiment of the invention, a second looper mechanism is provided between the stentering press machine and the plate reduction press machine, and can form a slack portion of the material to be shaped in a downward deflection, when the material is moving on the transfer line.
In any of the methods of manufacturing a hot rolled steel sheet according to the thirty-fourth through the thirty-seventh preferred embodiments of the present invention, the material to be shaped is heated to a predetermined temperature and sequentially pressed and reduced with upper and lower dies in the direction of its plate thickness and a plurality of upper and lower work rolls, thereby the material to be shaped is efficiently pressed, reduced and shaped.
In addition, between the dies for pressing, reducing and forming the thickness of the plate and the work rolls located adjacent to these dies, a slack portion of the material to be shaped is formed by an appropriate downward deflection to adjust for differences in the operating speeds of the dies for pressing the plate thickness and the work rolls for reducing the plate thickness, of the material to be shaped.
In the method of manufacturing a hot rolled steel sheet according to the thirty-seventh preferred embodiment of the invention, a slack portion of a material to be shaped is formed by an appropriate downward deflection between the dies for pressing, reducing and forming a plate in the direction of its width and the dies for pressing, reducing and forming a plate in the direction of its thickness, and adjusts for differences in the operating speeds for reducing the width with the former dies and reducing the plate thickness using the latter dies, of the material to be shaped.
In any one of the hot rolled steel sheet manufacturing apparatus according to any one of the thirty-eighth through the forty-second preferred embodiments of the present invention, the thickness of the material to be shaped, after heating in the tunnel furnace, is reduced sequentially by means of the dies of the plate reduction press machine and the work rolls of a plurality of roughing mills, thereby the material to be shaped is pressed, reduced and formed efficiently in the direction of the plate thickness.
In addition, a looper mechanism is provided between the plate reduction press machine and the first roughing mill in the upstream direction of the transfer line, and forms a slack portion in the material to be shaped in a downward deflection, and adjusts for differences in the operating speeds for reducing the plate thickness using the plate reduction press machine and reducing the plate thickness with the roughing mills, of the material to be shaped.
According to the hot rolled steel sheet manufacturing apparatus according to the forty-first preferred embodiment of the present invention, another looper mechanism is located between the stentering press machine and the tunnel furnace or between the tunnel furnace and the plate reduction press machine, as specified in claim 39 of the invention, and can form a slack portion in the material to be shaped in a downward deflection, when the material is moving on the transfer line.
The hot rolled steel sheet manufacturing apparatus specified in the forty-second preferred embodiment is, in addition to the conditions described in the fortieth preferred embodiment, provided with another looper mechanism located between the stentering press machine and the plate reduction press machine, and can form a slack portion in the material to be shaped in a downward deflection, when the material is moving on the transfer line.
According to the method of manufacturing a hot rolled steel sheet specified in the forty-third preferred embodiment of the present invention, aimed at achieving the fifth object of the invention, a material to be shaped is heated to a hot processing temperature and moved from the upstream side to the downstream side of a transfer line, a plurality of dies located along the direction of the transfer line are moved alternately towards and away from the material to be shaped, from above and below the material to be shaped, thus the material to be shaped is processed and formed in the direction of the plate thickness, by means of a plurality of plate thickness reducing operations, then the material after being reduced in the direction of the plate thickness by a plurality of plate thickness reducing operations is rolled by work rolls from above and below the material to further reduce and form the material in the direction of the plate thickness, and a slack portion in the material being shaped is formed in an appropriate downward deflection between the last dies in downstream direction of the transfer line and the work rolls.
The hot rolled steel sheet manufacturing apparatus according to the forty-fourth preferred embodiment is provided with a heating and holding furnace for heating a material to be shaped, located on a transfer line, a plate reduction press machine comprised of a plurality of upper and lower dies located opposite each other above and below the transfer line, and in series in the longitudinal direction of the transfer line, that can press and reduce the material to be shaped in the direction of the plate thickness, and the aforementioned plate reduction press machine being located on the downstream side of the heating and holding furnace on the transfer line, a roughing mill composed of work rolls located opposite each other above and below the transfer line, on the downstream side of the above-mentioned plate reduction press machine on the transfer line, that can roll the material to be shaped in the direction of the plate thickness, and a looper mechanism located between the aforementioned plate reduction press machine and the roughing mill, that can form a slack portion in the material to be shaped in a downward deflection.
In the hot rolled steel sheet manufacturing apparatus according to the forty-fifth preferred embodiment of the present invention, which is a modified form of the forty-fourth preferred embodiment, the looper mechanism is composed of an upstream table located in the vicinity of the plate reduction press machine in the downstream direction of the transfer line, means for raising and lowering the aforementioned upstream table, a plurality of upstream rollers installed on the above-mentioned upstream table in such a manner that the upstream rollers can contact the lower surface of the material to be shaped and the positions of the bearings supporting the rollers gradually slope downwards in the downstream direction of the transfer line, upstream pinch rolls located in the vicinity of aforementioned upstream table in the upstream direction of the transfer line, that can grip the material to be shaped in the direction of the plate thickness, a downstream table located in the vicinity of the roughing mill in the upstream direction of the transfer line, a plurality of downstream rollers installed on the above-mentioned downstream table in such a manner that the downstream rollers can contact the lower surface of the material being shaped and the positions of the bearings supporting the rollers gradually slope downwards in the downstream direction of the transfer line, and downstream pinch rolls located in the vicinity of the aforementioned downstream table in the downstream direction of the transfer line, that can grip the material being shaped in the direction of the plate thickness.
When a hot rolled steel sheet is manufactured by the method specified in the forty-third preferred embodiment of the present invention, a material to be pressed, reduced and shaped is heated to a hot processing temperature, its thickness is reduced several times by a plurality of upper and lower dies arranged along the transfer line, and then the portion of the material to be shaped, that has been subjected to several operations to reduce its thickness, is further pressed, reduced and formed in the direction of the plate thickness with upper and lower work rolls, thereby the material to be shaped is pressed, reduced and formed efficiently in the direction of the plate thickness.
Furthermore, a portion of the material to be shaped, whose plate thickness has been reduced completely through several operations, is formed into slack downward deflection between the last dies in the downstream direction of the transfer line and the work rolls, so as to contain a portion of the material to be shaped, already output after being pressed with the dies.
In any of the hot rolled steel sheet manufacturing apparatus according to the forty-fourth or the forty-fifth preferred embodiments of the present invention, a material to be pressed and shaped is heated in the heating and holding furnace, pressed in the direction of its plate thickness by a plurality of dies arranged along the transfer direction of the plate reduction press machine, and the portion of the material to be shaped, that has been pressed, reduced and formed completely by the plate reduction press machine, is pressed, reduced and formed in the direction of the plate thickness using the work rolls of the roughing mill, thus the material to be shaped is efficiently reduced, pressed and formed in the direction of the plate thickness.
In addition, a portion of the material to be shaped, already pressed, reduced and formed by the plate reduction press machine, is deflected downwards to form a slack portion using the looper mechanism, that contains a portion of the material to be shaped, after it has already been pressed by the plate reduction press machine.
6. The sixth object of the present invention is to adjust the width of a slab as well as to prevent cracks at the edges or the occurrence of seam flaws. The object also includes the prevention of slipping between the dies of the press machine and the slab.
To achieve the sixth object described above, the forty-sixth preferred embodiment of the present invention provides a rough pressing apparatus with an edger for pressing a slab in the lateral direction thereof, located at the inlet of a press machine.
When a slab is pressed and reduced in the lateral direction with an edger, any gaps, voids, etc. existing inside the edges of the slab, which may possibly cause cracks later, are compressed, so that even if the slab is later pressed and reduced in the direction of the thickness with a press machine, cracks or flaws may not be produced so easily. Hence, the edger can prevent the occurrence of cracks or flaws as well as adjusting the width of a slab. In addition, as the stentering rolls of the edger rotate, they have the effect of pushing the slab into the press machine. In addition, because of the rotation of the stentering press rolls, slippage between the surfaces of the dies that slope in the longitudinal direction of the slab and the slab can also be prevented.
According to the forty-seventh preferred embodiment of the invention, the above-mentioned edger is provided with cylindrical rolls that press the lateral edges of the slab while the rolls are rotating.
Because the cylindrical rolls compress any gaps etc. that if present in the slab, may cause cracks, by pressing the lateral edges of the slab, therefore even when the slab is later pressed and reduced in the direction of its thickness with a reduction press machine, cracks or flaws will not be produced so easily. Although the edges become thicker at this time, no cracks will be created when the slab is pressed in the direction of its thickness, because the slab has been compressed by being pressed and reduced in the lateral direction.
According to the forty-eight preferred embodiment of the invention, the center portions of each of the cylindrical rolls is provided with a projecting portion with a convex cross section, formed on the peripheries of the cylindrical rolls.
The projecting portion of the rolls produces a linear recess at the center of the surface of the lateral edge of a slab, therefore afterwards when the thickened edges of the slab are pressed and reduced in the direction of the thickness using a plate reduction press machine, the linear recesses can compensate for the excess volume of the slab, so that pressing to reduce the thickness can be carried out smoothly.
According to the forty-ninth preferred embodiment of the invention, the edger is provided with bobbin-shaped rolls that press the edges of the slab while the rolls are rotating, and each of the bobbin-shaped rolls has a cylindrical center portion, tapered portions connected to both ends of the center portion, and outer cylindrical portions connected to the outsides of the tapered portions.
When the bobbin-shaped rolls press a slab in the lateral direction, the lateral edges of the slab can be formed in a shape with vertical surfaces at the center and sloping surfaces at the top and bottom. As a result, the shape of the edges can prevent the large build-ups which would otherwise be produced when the slab is later pressed with the reduction press machine in the direction of the thickness. Therefore, edge cracks and seam flaws, that may otherwise arise during later pressing and rolling in the direction of the thickness, can be prevented.
In the fiftieth preferred embodiment of the invention, projecting portions with convex cross sections are formed on the peripheries of the cylindrical portions of the bobbin-shaped rolls.
The projecting portions of the rolls produce linear recesses at the centers of the surfaces of the lateral edges of a slab, and the linear recesses absorb the build-ups produced at both edges, when the slab is later pressed and reduced in the direction of its thickness by a plate reduction press machine, therefore pressing and reducing the thickness can be carried out smoothly.
According to the fifty-first preferred embodiment of the invention, in which the aforementioned plate reduction press machine and the above-mentioned edger are combined, the rolling speed of the edger is made identical to the speed of conveying the slab during a period when there is no pressing, and the aforementioned rolling speed is made equal to the speed at which the slab is conveyed during a pressing period, minus the speed at which the material of the slab is forced backwards during pressing.
The plate reduction press machine is constructed as a flying press machine in which a slab is also conveyed while it is being pressed. Although the slab extends longitudinally when pressed, the speed at which the slab is forced backwards, that is, in the reverse direction to the transfer direction of the slab (in the direction of the edger) is called the backward speed. The rolling speed of the edger is adjusted to be equal to the speed of conveying the slab during the period when there is no pressing, and it is made equal to the speed at which the slab is conveyed during pressing minus the backward speed due to pressing, thereby both the width and thickness can be pressed and reduced simultaneously.
7. The seventh object of the present invention is to offer a hot rolled steel sheet manufacturing apparatus that can sequentially press the width and thickness of a slab.
To achieve the seventh object as described above, according to the fifty-second preferred embodiment of the present invention, a stentering press machine and a thickness reduction press machine are installed along a line on which a slab moves, a width pressing operation and a thickness pressing operation are carried out such that they operate at different times, the speed at which the slab is moved during the width pressing operation is made identical to the speed at which the pressing unit of the stentering press machine is moved, and the speed at which the slab is moved during the thickness pressing operation is made identical to the speed at which the pressing unit of the thickness press machine is moved.
By installing the stentering and thickness press machines along the line on which the slab moves, and by actuating the stentering and thickness pressing operations at different times, each pressing operation can be carried out without adversely affecting the other machine. In addition, because the slab is moving even during the stentering pressing or thickness pressing period, continuous pressing or rolling can be performed. In this way, reversing operation is not required for either press machine.
According to the fifty-third preferred embodiment of the invention, a stentering press machine and a thickness reduction press machine are provided and located along a line on which a slab is transferred, in which the aforementioned stentering press machine is composed of a first pressing device that moves in the direction of flow of the slab, together with the slab during a stentering period, the above-mentioned thickness reduction press machine is provided with a second pressing device that moves in the direction of flow of the slab, together with the slab during a thickness pressing period, and the aforementioned stentering and thickness reduction press machines are operated at different times.
The pressing unit of the stentering press machine moves in the direction of flow of the slab together with the slab during a stentering pressing period, and the pressing unit of the thickness reduction press machine also moves in the direction of flow of the slab together with the slab when it is being pressed in the direction of its thickness, and the slab moves at the normal conveying speed when neither unit is operated, therefore the slab can be rolled continuously. In addition, since a stentering pressing operation and a thickness reduction pressing operation are actuated at different times instead of being carried out simultaneously, they have no adverse effect on each other.
In the fifty-fourth preferred embodiment of the invention, the distance L for moving a slab in one cycle of the stentering period, the thickness reduction pressing period, and the period for conveying at the normal speed, as specified in the fifty-third preferred embodiment, is no larger than either the length L1 of the stentering dies in the direction of flow of the slab or the length L2 of thickness reduction pressing dies in the direction of flow of the slab.
Although the slab is fed by a length L in one of the above cycles, L is not larger than either the length L1 of the stentering dies or the length L2 of the thickness reduction pressing dies, both in the direction of flow of the slab, therefore both the lengths pressed by the stentering press and by the thickness reduction press in the next cycle slightly superimpose the corresponding lengths pressed in the previous cycle. Consequently, the slab can be properly pressed in the stentering direction and the thickness direction without leaving any unpressed portions.